Electrical power grids include power generation stations, high-voltage transmission grids, and lower-voltage distribution grids. Step-up transformers at the generating stations provide high-voltage (over 100 kV) power to the transmission grid for efficient long-distance power transmission. Step-down transformers at distribution substations convert the high-voltage power to lower-voltage power that is distributed over shorter distances for local use. These transformers are associated with loads such as buildings, commercial and industrial enterprises. Because transformers are a key component of electrical power grids, transformer malfunction and failure is a serious concern. Accordingly, there is a need for techniques and devices for monitoring power transformer condition. Moreover, because of significant expenses are required for aging power transformer replacements, there is a need for power transformer diagnostics to assist in the increase in power transformer lifetimes.